1. Field of the Invention
The present invention relates to the technology field of exhaust mufflers, and more particularly to a waste air exhausting device having functionality to abate noise and modulate noise frequency.
2. Description of the Prior Art
Because a high-level noise would be produced during an engine of a motor or a motorcycle directly exhausting a waste air, it is necessary to treat the water air with a noise reducing process by using an exhaust silencer connected to exhaust port of the engine before the waster air is exhausted into air.
Please refer to FIG. 1, which illustrates a cross sectional view of a conventional exhaust silencer. As FIG. 1 shows, the conventional exhaust silencer 1′ is constituted by a housing 10′, an air inlet pipe 2′, a communication pipe 3′, an air outlet pipe 4′, and a helical rod 5′, wherein the inlet pipe 2′ has a first air inlet 21′ extending out of one end of the housing 10′ for connecting with engine's exhaust port, and the air outlet pipe 4′ has an exhaust outlet 42′ extending out of the other end of the housing 10′. In addition, a first expansion chamber 11′ is formed in the housing 10′ for simultaneously communicating a first air outlet 22′ of the inlet pipe 2′ and a second air inlet 31′ of the communication pipe 3′. Besides the first expansion chamber 11′, a second expansion chamber 12′ is also formed in the housing 10′ or simultaneously communicating a second air outlet 32′ of the communication pipe 3′ and a third air inlet 41′ of the air outlet pipe 4′. Moreover, a third expansion chamber 13′ is formed in the housing 10′ and disposed between the first expansion chamber 11′ and the second expansion chamber 12′.
As FIG. 1 shows, in order to enhance the noise reduction efficiency of the exhaust silencer 1′, a sound-absorbing material 30′ is particularly adopted to cover a plurality of first perforations 24′ formed on the side wall of the inlet pipe 2′ and a plurality of second perforations 34′ formed on the side wall of the communication pipe 3′. By such arrangements, the waste air would flow into the first expansion chamber 11′ of the housing 10′ for being treated with a first decompressional expansion process after being outputted by the engine and continuously flowing into the inlet pipe 2′. Furthermore, the waster air subsequently flows into the second expansion chamber 12′ via the communication pipe 3′ so as to be treated with a second decompressional expansion process; meanwhile, parts of waste air in the inlet pipe 2′ and the communication pipe 3′ would flow into the third expansion chamber by passing through the first perforations 24′ and the second perforations 34′, so as to be treated with a mixed decompression process. Eventually, after a noise muffling treatment is completed by the sound-absorbing material 30′ to the waste air, the waste air is then converted to a vortex air flow by the hollow helical rod 5′ and a plurality third perforations 511′ formed on multi helical blades 51′ of the helical rod 5′.
Although current motors or motorcycles have conventionally equipped with the exhaust silencer 1′ shown in FIG. 1 for noise reduction, inventors of the present invention still find the conventional exhaust silencer 1′ showing drawbacks and shortcomings in practical applications, wherein the drawbacks and shortcomings are listed as follows:    (1) The exhaust silencer 1′ mainly utilizes discontinuous section areas (i.e., the perforations 24′, 34′ and 511′) and the sound-absorbing material 30′ to abate and muffle noise, so that the noise abatement efficiency of the exhaust silencer 1′ is up to 6 dB. However, the noise abatement technology applied in the exhaust silencer 1′ may cause engine's exhaust backpressure increase, such that the horsepower and the fuel consumption of the engine are hence decreased and increased, respectively.    (2) Moreover, engineers skilled in the noise-cancelling technology fields have known that the noise abatement technology applied in the exhaust silencer 1′ is called passive noise reducing method, and the method can merely carry out a good noise reduction efficacy on those noises with frequencies over 500 Hz. However, most of frequencies carried by the noises produced during the engines of motors or motorcycles exhausting waste air are lower than 500 Hz, that means the said passive noise reducing method cannot effectively abate and muffle the noise produced by motor's or motorcycle's engine.    (3) The most important is that, because the exhaust silencer 1′ is constituted by a housing 10′, an air inlet pipe 2′, a communication pipe 3′, an air outlet pipe 4′, a helical rod 5′, and multi sound-absorbing materials 30′, the exhaust silencer 1′ includes some natural drawbacks such as heavy weight, large volume and hard to be assembled.
Accordingly, in view of the conventional exhaust silencer 1′ showing many drawbacks and shortcomings in practical applications, the inventors of the present application have made great efforts to make inventive research thereon and eventually provided a waste air exhausting device having functionality to abate noise and modulate noise frequency.